Objective 1: One long term goal is to identify tests that accurately detect middle-ear dysfunction in infants. Wideband (WB) measurements of middle-ear function in infants may overcome limitations of conventional single-frequency middle-ear assessment techniques. Aim 1 of the proposed study evaluates the test performance of conventional 1-kHz tympanometry and WB middle-ear tests (e.g. reflectance, admittance) in terms of their ability to correctly classify pass or refer outcomes on an outpatient otoacoustic emission (OAE) re-screening test. Test performance will be evaluated using clinical decision theory analysis. Identification of a valid test of middle-ear function, which might be used during the newborn hearing screening and follow-up re-screening, would 1) help health care professionals more accurately interpret and communicate OAE and auditory brainstem response (ABR) screening and re-screening test results and 2) improve the accuracy of middle-ear assessment, enabling more informed decisions regarding recommendations for additional diagnostic testing and/or referrals for medical care. Objective 2: Another long term goal is to better understand the effects of age-related changes in the ear-canal and middle-ear on forward and reverse sound transmission between the ear canal and cochlea. Differences in infant and adult OAE responses have been explained by ear-canal and middle-ear effects, but only at 6 kHz. Aim 2 of the proposed study investigates infant middle-ear transmission characteristics using forward and reverse transfer functions between the ear canal and cochlea based on measurements of distortion product (DP) OAEs. Specifically, DPOAE input/output (I/O) functions will be obtained at half-octave frequencies from 1.5 to 8 kHz in adults and young infants with normal hearing function. A model, generated to fit adult DPOAE I/O functions will be used to fit infant functions to calculate forward and reverse transmission gain between the ear canal and cochlea. Changes in transmission gain will be evaluated in infants relative to adults, and across frequency in infants. This information may 1) help interpret age-related changes in OAE responses and 2) inform studies of infant speech perception and hearing sensitivity with regard to potential ear-canal/middle-ear effects. [unreadable] PUBLIC HEALTH RELEVANCE: Results from this study may help improve clinical procedures for the diagnosis and treatment of middle-ear dysfunction in infants. Also, information about how the ear canal and middle ear influence sound as it travels in and out of the ear may help explain developmental differences in clinical hearing test results. [unreadable] [unreadable] [unreadable] [unreadable]